Research objectives of this study are to conduct a broad investigation of the physiological role of atrial receptors. This will be done by a variety of methods. We plan to study the reflex effects elicited by selective distension of a portion of the atrial wall of the conscious dog. We also plan to examine the changes in atrial receptor activity which occur during cardiac arrhythmias in the anesthetized dog and to determine whether reflex changes in renal function occur as a result or cardiac arrhythmias. We further plan to determine whether the renal response to atrial tamponade persists in dogs with total cardiac denervation. Finally, we propose to examine the effector mechanisms which act on the kidney to produce the diuresis which is elicited by tachycardia.